It is axiomatic that biological systems can be better understood if we understand both their structure and their histories. This proposal, directed towards the NIAAA and NIEHS, will provide the first example where historical biology is applied to an area of interest to these institutes: the evolution of the response of primates to environmental ethanol. Using an innovative combination of molecular evolution, paleontology, organic chemistry, kinetics, molecular biology, biotechnology, and crystallography, this research will yield a model that describes, from the biomolecule to the pathway, the adaptive response of primates, including humans, as they encountered, managed, and ultimately exploited a new environmental toxin, ethanol, over the past 100 million years. Our work will focus on the evolution of the alcohol dehydrogenase-aldehyde dehydrogenase (ADH-AlDH) system in primates. These enzymes form a two-step pathway that yields acetate from ethanol. Genes for these enzymes hold genetic variation in human populations that correlates with many alcohol-related diseases. We will first collect primate sequences to enrich the evolutionary models for these two superfamilies of proteins, including trees, alignments, ancestral sequences, and computational analyses of functional change within these superfamilies. These will be followed by paleogenetic experiments, where ancestral ADHs and AlDHs from human ancestors and relatives will be resurrected for study in the laboratory. Detailed analyses of substrate specificity and kinetic power will let us determine whether our ancestors followed "avoidance", "accommodation", or "utilization" strategies to manage ethanol when it first emerged, and thereafter as ethanol increased and decreased in the ecosystems of primates, until the present. These will be supplemented by analyzing the evolution of the "systems biology" properties of the system. The results will help us better understand the meaning in human biology of data collected in model organisms (e.g. rat, fly), which are separated from humans by hundreds of millions of years. Finally, we will use reductionist science, including protein crystallography, to describe at a molecular level what Darwinian processes did to manage this environment-genomics dynamic. This research will be the first collaboration between Steven Benner, who initiated experimental paleogenetics as a field and has developed planetary and systems biology in many biomolecular systems [Ben02], and Thomas Hurley, who has comprehensively studied human ADHs and AlDHs [Hur01]. In addition to producing a combined historical and reductionist analysis of this system, this work will provide a paradigm showing how this combination can be applied throughout biomedical research, and therefore have an impact on nearly every system of interest to human biology. Although it is axiomatic that diseased and healthy biology can be better understood if we understand its natural history, historical science has had difficulty entering the mainstream of biomedical research funding. This proposal, directed towards the NIAAA and NIEHS, seeks funding to support a collaboration between two laboratories to develop a detailed historical model for the evolution of the alcohol dehydrogenase-aldehyde dehydrogenase (ADH-AlDH) system in primates and closely related mammals. By combining natural history and reductionist science, the work will show how the substrate specificities and catalytic activities of these two enzymes co-evolved in response to changing environmental conditions, as the exposure of this environmental toxin changed. This will provide the first paradigm applying evolutionary analysis to an important medical problem, thereby encouraging the application of such analyses throughout medical research, where they are expected to have significant impact wherever they are applied.